This invention pertains generally to optical transceivers and, in particular, to an optical device package for an optical transceiver.
Optical transceivers are known in the art and include active optical devices or diode packages. Common diode packages include LED packages such as a TO-46 package or a laser diode package such as RLD-85PC diode package by Rohm, Incorporated. These diode packages or TO cans typically include a metallic housing having a laser diode or LED for transmitting data and a photo diode for performing power-monitoring, metal contact leads exiting from the diodes for connection to a power source and a cover glass opposed to the diode, through which the energy is transmitted. The TO can is hermetically sealed. The hermetic sealing of the TO can is a time-consuming and expensive process which adds to the overall expense of the LED or laser package. As well, the commonly known TO cans do not have the emission area of the diode aligned within the TO can in a consistently centered orientation. Thus, placement of the TO can in a uniform position does not provide for alignment of the diode to an optical connector and maximum power transmission is not achieved. Thus, alignment of the TO package becomes a time-consuming and expensive process.
Commonly known housings for optical transceivers require complex mechanical means in order to align the diode package, the lens, the bore and the optical waveguide ferrule. Mechanical means, such as a screw is commonly used to actively align the TO can within the housing.
Further, a molded plastic housing is often used having precision molded cavities specifically sized for receiving a diode package, another cavity specificaliy sized for receiving a lens and another cavity specifically sized for receiving an optical waveguide ferrule. Such an optical transceiver housing is often rendered ineffective in production due to variations in the alignment of the LED or laser relative to the TO can.
In view of the above, it is an object of the present invention to provide an optical device package which is quickly and inexpensively manufactured.
It is a further object of the present invention to provide an optical device package, which may be easily aligned with an optical transceiver housing.
It is another object of the present invention to provide an optical package having a single optical axis.
It is another object of the present invention to provide an optical package housing formed using insert molding techniques in order to provide a quickly and inexpensively manufactred precision housing assembly.
A principal object of this invention is to provide an optical package comprising a housing including a bore for receiving an optical waveguide and a focusing element adjacent the bore, the bore and the focusing element being aligned along a common optical axis, a diode mounted to a substrate adjacent the focusing element and an alignment means associated with the housing for aligning the substrate along the optical axis. The alignment means may include a trace located in a predetermined position on the substrate to which the housing is mounted. The alignment means may include a groove located in a predetermined position on the substrate to which the housing is mounted. The housing may include an outer sleeve defining the bore for receiving an optical waveguide and an inner sleeve for receiving the focusing element. The inner sleeve may include a lens support means for mounting the focusing element. The focusing element may be mounted in a lens support means. The lens support means may include a plastic washer having a bore of a diameter less than the diameter of the focusing element. The focusing element may be a ball lens. The groove may be formed between conductive traces adhered to the substrate. The groove may be integrally molded with the substrate. The bore may have a diameter of approximately 0.0984 inches or greater. The height of the inner sleeve may be less than the height of the outer sleeve. The inner sleeve may be partially filled with an optical filler composition. The alignment means may include a precision formed aperture in the housing for receiving the substrate. The substrate may be a precision formed material having a predetermined size and the diode mounted thereto in a predetermined orientation on the substrate. The focusing element may be integrally molded with the housing. The housing and the focusing element may be formed of a transmissive material allowing for the transmission of wavelengths from 780-1350 nanometers.
In an embodiment, an optical package is provided comprising a substrate having a diode mounted thereto and a groove formed in the substrate surrounding the diode, an inner sleeve mounted within the groove having a lens therein and an outer sleeve mounted to the substrate surrounding the inner sleeve for receiving an optical ferrule. The groove may be formed between conductive traces adhered to the substrate. The groove may be integrally molded with the substrate. The inner sleeve may include a tab protruding within the sleeve to provide support to the lens. The inner sleeve may be formed of stainless steel, brass, nickel silver or ARCAP(copyright). The outer sleeve may have a cylindrical shape and include a bore having an inner diameter of 0.0984 inches or greater. The height of the inner sleeve may be less than the height of the outer sleeve. The diode may be a surface emitting diode. The diode may be an LED. The diode may be a vertical cavity surface emitting laser (VCSEL). The diode may be a photodiode. The inner sleeve may be partially filled with an optical filler composition. The optical filler composition may be an epoxy or a silicone composition. The optical filler composition may form a meniscus at the base of the lens to provide retention of the lens. The tabs of the inner sleeve may be formed from portions of the inner sleeve wall which are punched from the wall and protrude within the interior of the inner sleeve. The optical package may include a single optical axis wherein the diode has an emission point providing an emission axis upon which the lens and the ferrule are aligned.
In an embodiment, an optical package is provided comprising a substrate having an outer trace forming a circle and a pair of circular concentric inner traces formed within the outer trace and the pair of concentric inner traces defining a groove therebetween, an inner cylindrical sleeve mounted within the groove including a tab punched from the sidewall of the inner sleeve protruding toward the center of the cylindrical inner sleeve, a surface emitting diode and lens mounted within the inner sleeve and an outer cylindrical sleeve mounted on the outer trace defining an inner bore having a diameter of 0.0984 inches or greater and having a height greater than the inner sleeve. The inner traces may be formed from conductive copper traces. The diode may be mounted to the substrate. The lens may be a ball lens supported by the tab of the inner sleeve.
In an embodiment, an optical package is provided comprising a housing including a bore for receiving an optical waveguide, a focusing element adjacent the bore and a precision formed aperture for receiving a substrate, the bore, the focusing element and the aperture being aligned along a common optical axis and a diode mounted to the substrate. The substrate may be a precision formed material having a predetermined size and the diode mounted thereto in a predetermined orientation on the substrate. The substrate may be formed of a silicon material. The focusing element may be integrally molded with the housing.
A method of assembling an optical package is provided including the steps of forming a housing having a bore and a focusing element adjacent the bore, the focusing element and the bore aligned along a common optical axis, mounting a diode to a substrate in a predetermined position and mounting the substrate to the housing so that the diode is centered on the optical axis. The method further including the steps of forming an alignment means on the substrate or the housing and mounting the substrate to the housing via the alignment means. The method further including the steps of forming the alignment means of a precision aperture in the housing and receiving a precision formed substrate in the aperture.
The method further including the steps of forming a groove on a substrate surrounding a central point, mounting the diode at the central point of the substrate, mounting an inner sleeve within the groove, securing the inner sleeve to the substrate, mounting the focusing element within the inner sleeve, placing an outer sleeve on the substrate surrounding the inner sleeve, aligning the outer sleeve along the optical axis and securing the outer sleeve to the substrate. The method of assembling the optical package may include the step of injecting an optical filler composition into the inner sleeve after the lens is inserted therein. The method of assembling the optical package wherein the outer sleeve is mounted on an outer conductive trace adhered to the substrate and the outer sleeve is secured thereto via solder. The method of assembling an optical package wherein the outer sleeve may be integrally molded with the lens and inner sleeve. The method of assembling an optical package wherein the outer sleeve is actively aligned by inserting a ferrule of an optical waveguide attached to a power meter and to the bore of the outer sleeve, adjusting the outer sleeve laterally until a desired power level is achieved and securing the outer sleeve to the substrate.
As noted, an optical package can be made of molded plastic having precision molded cavities formed therein. Additional embodiments take advantage of the many special properties of a plastic housing, providing additional alternate mechanisms for aligning a bore, a focusing element, and a substrate having an optical diode mounted thereon. In an embodiment, the housing is formed with a first bore for receiving an optical waveguide in the form of a fiber optic connector ferrule surrounding an optical fiber. A second bore, or more generally a base cavity, is formed in the base of the housing opposite the first bore. The base cavity is configured to receive a focusing element and an optical element, such as a VCSEL, LED, or photodiode. A smaller internal cavity is formed at the end of the base cavity, and acts as a support means for the focusing element. A small through hole communicates between the focusing element support cavity and the first bore, allowing optical radiation to pass from the focusing element to an optical waveguide inserted into the first bore. Mounting posts extend from the base of the housing, circumferentialy spaced around the base cavity. The optical element is mounted to a separate substrate having alignment holes formed therein. The alignment holes are positioned to receive the mounting posts extending from the base of the housing, and are formed having a larger diameter than the posts such that the substrate can be maneuvered relative to the housing to facilitate alignment of the various optical components. Alignment is performed actively, and when the maximum amount of optical radiation is coupled to the optical waveguide, the posts are bonded to the substrate to hold the housing in place and maintain proper alignment.
Optional bonding methods include reflowing the plastic posts using a CO2 laser, infared heat source, hot air, or some other means of heating and melting the plastic posts. Using this technique the mounting posts are melted and the molten plastic reflows into the alignment holes, filling the spaces between the posts and the substrate. After completely filling the alignment holes, the excess plastic from the melted posts forms a meniscus or mushroom shaped dome of material over each alignment hole. Upon cooling, the plastic hardens to form a secure bond between the housing and the substrate. A similar method for adhering the housing to the substrate involves heating the plastic posts, but rather than fully melting and reflowing the posts, either a rivet forming tool or a compressive blast of hot air is used to compress the posts into the proper mushroom shaped dome necessary to secure the substrate to the housing. A third method for bonding the housing to the substrate involves hot melting an epoxy into the alignment holes and allowing the epoxy to bond the two pieces together. Finally, a fourth method involves forming the substrate itself out of a plastic material similar to that used for the housing, and laser welding the two pieces together. While the methods disclosed herein are preferred, it should be clear to those skilled in the art that other bonding methods may be employed without deviating from the novel aspects of the present invention.
In another embodiment incorporating a plastic housing, the plastic housing is identical to that described previously, except the mounting posts are omitted. In their place, a circular metal insert is inserted into the base cavity of the housing. The metal insert is formed with an annular flange, which engages the base of the housing to provide a positive stop against excessive insertion of the insert into the housing. Surface features such as a knurled finish, barbed teeth, or threads, or some other friction enhancing feature, are formed on the outer surface of the insert so that upon insertion into the housing, the insert frictionally engages the side walls of the housing. The optical device is mounted on a substrate, which is either partially or entirely formed of metal. Minimally, the edges of the substrate are metallized to facilitate bonding the substrate to the metal insert The substrate is placed over the annular flange and the optical components actively aligned. Upon proper alignment of the optical components, the metallized edges of the substrate are bonded to the annular flange of the metal insert by laser welding, soldering, or other known techniques for bonding metal components. In an alternate arrangement, the metal insert engages the outer surface of the housing forming somewhat of a metal cap over the optics cavity, but having a circular aperture formed in the end thereof for receiving the optical element. Again, surface features formed on the mating surface of the insert frictionally engage the outer surface of the housing to form a tight interference fit therewith.
In an embodiment, the lens cavity is formed immediately adjacent the optics cavity, and retning features are molded into the lens cavity around the opening joining the lens cavity to the optics cavity. The retaining features act to hold the focusing element within the lens cavity. The retaining features are slightly compressible so that the focusing element can be press fit into the cavity past the retaining features. When the focusing element is fully inserted past the retaining features, the retaining features expand to their natural extent, thereby capturing the focusing element within the lens cavity.
In yet another embodiment, the retaining features include a pitched annular wall surrounding the lens cavity. Externally the pitched wall is supported by a plurality of plastic support buttresses, which add rigidity to the wall. The wall defines a lens cavity where the entrance to the cavity is narrower than the base of the cavity, and the diameter of the focusing element itself.
In another, similar embodiment, the lens cavity is formed immediately adjacent the ferrule receiving bore. The focusing element is insertable into the lens cavity through the ferrule receiving bore. Compressible retaining features are molded into the lens cavity around the opening joining the lens cavity to the ferrule receiving bore.
In a further embodiment, a plastic housing provides an improved mechanism for aligning the mating optical waveguide with the plastic optical package. A split bore feature is incorporated with a first optical waveguide receiving bore. The split bore embodiment contemplates at least one narrow slot formed in the optical waveguide receiving bore, extending from the receiving end of the bore toward the base of the bore near the point where a focusing element is mounted. The slot or slots allow the walls of the housing to flex as the waveguide is inserted into the bore. Precision alignment of the waveguide is only necessary at the base end of the bore adjacent the focusing element. The flexibility of the bore sidewalls diminishes toward the end of the slots. Thus, as an optical waveguide is inserted into the bore, the increasing rigidity of the sidewalls gradually forces the waveguide to the precision alignment position at the base of the bore. This arrangement has the advantages of simplifying the mating procedure of the waveguide to the housing, and reducing the area of precision molding necessary to properly align the waveguide, thereby reducing the cost of molding the plastic housing.
In a further embodiment of the invention a plastic housing having a ceramic sleeve inserted therein to form a ferrule receiving bore wherein the ceramic sleeve is insert molded within the plastic housing. The housing includes a ball lens therein. The ball lens is insert molded within the housing. The housing includes a mounting ring at the end opposed to the ferrule receiving end. The mounting ring is insert molded to the plastic housing.
These and other features of the invention are set forth below in the following detailed description of the presently preferred embodiments.